The thing that both amuses and bemuses me most about theories like these, is that they seem entirely dedicated to missing the forest for the trees. That is, they focus on some pivotal event - the JFK assassination, the moon landings, 9/11 etc. - and instead of working on a big picture theory, one that ties with economic conditions, clear political agendas etc., they spend all their effort on fine-combing the event itself.

It's an exercise in nitpicking, while the overall framework is typically some generic nefarious scheme for world domination, for... reasons. Because the nigh-omnipotent powers that be apparently have nothing better to do than controlling Billy Bob in his homemade bunker, or some guy who calls himself L33T H4XX0R G3N1US online, while still failing to understand the benefits of showering at least once a week.

For comparison, let's say that in 1914, Archduke Franz Ferdinand wasn't assassinated by Gavrilo Princip, but by... Lenin's third cousin twice removed, or something. Even if there's tons of evidence supporting that claim, the question remains - who cares? Who gives a shit? Because half the European countries were already looking for an excuse - any excuse - to go at each other's throats. Whether it was Princip killing Ferdinand with a pistol in Sarajevo, or Grigori Rasputin's zombie corpse killing Sultan Mehmet V with a ham sandwich in Vienna, the aftermath of that Clue game would be the same. The momentum was already there, and any otherwise minor event would be used to harness it.

And the same goes for 9/11. Simple fact is, Americans need a major war roughly once every 25 years, in order to balance their lopsided economy. From that point on, any excuse will do. If anything, it's only too easy to just order/allow a few fanatical idiots to hijack a couple of planes, aim them at the one pair of skyscrapers in New York that are built with the support structure on the outside (meaning a plane-sized breach would indeed force them to collapse on themselves, whereas something like the Empire State or Chrysler buildings would remain standing), and just let the dominoes fall on their own.

The bottom line is, events like these aren't like episodes of Columbo, where a couple of stray facts lead to the bad guys dramatically confessing their guilt in the final act. Most of the time, they're distractions leading to wild goose chases, without building up to an actually useful general theory with some predictive quality. Really, what's the conclusion of the "no plane" version, versus any other "inside job" theory? At most, it means ILM got a great gig doing special effects for the government. Big political difference.